Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods

Meehl, Gerald A.; Arblaster, Julie M.; Fasullo, John T.; Hu, Aixue; Trenberth, Kevin E.

doi:10.1038/nclimate1229

Cited by 645 publications

(571 citation statements)

References 25 publications

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“…The historical experiment ensemble mean shows a 1.0 day per year decrease over the same period. This decrease is despite the decadal La Niña-like trend (Meehl et al 2011), which might have caused an increase of mild weather in the absence of radiative forcing. The near future projected decrease of mild weather (2016-2035) based on RCP4.5 is consistent.…”

Section: Changes In the Recent Pastmentioning

confidence: 93%

Shifting patterns of mild weather in response to projected radiative forcing

2017

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Climate change has been shown to impact the mean climate state and climate extremes. Though climate extremes have the potential to disrupt society, extreme conditions are rare by definition. In contrast, mild weather occurs frequently and many human activities are built around it. We provide a global analysis of mild weather based on simple criteria and explore changes in response to radiative forcing. We find a slight global mean decrease in the annual number of mild days projected both in the near future (−4 days per year, [2016][2017][2018][2019][2020][2021][2022][2023][2024][2025][2026][2027][2028][2029][2030][2031][2032][2033][2034][2035] and at the end of this century (−10 days per year, 2081-2100). Projected seasonal and regional redistributions of mild days are substantially greater. These changes are larger than the interannual variability of mild weather caused by El Niño-Southern Oscillation. Finally, we show an observed global decrease in the recent past, and that observed regional changes in mild weather resemble projections.

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Section: Changes In the Recent Pastmentioning

confidence: 93%

Shifting patterns of mild weather in response to projected radiative forcing

2017

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“…Consequently, this remains an important phenomenon that still requires an explanation. It could also be associated with some of the explanations advanced for the hiatus of global warming [158][159][160].…”

Section: Regional Projections and Emergence Time Of The Forced Signalmentioning

confidence: 95%

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Clark

Church

Gregory

et al. 2015

Curr Clim Change Rep

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Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5's assessment of (i) historical sea level rise, including attribution of that rise and implications for the sea level budget, (ii) projections of the components and of total global mean sea level (GMSL), and (iii) projections of regional variability and emergence of the anthropogenic signal. In each of these cases, new work largely provides additional evidence in support of the AR5 assessment, providing greater confidence in those findings. Recent analyses confirm the twentieth century sea level rise, with some analyses showing a slightly smaller rate before 1990 and some a slightly larger value than reported in the AR5. There is now more evidence of an acceleration in the rate of rise. Ongoing ocean heat uptake and associated thermal expansion have continued since 2000, and are consistent with ocean thermal expansion reported in the AR5. A significant amount of heat is being stored deeper in the water column, with a larger rate of heat uptake since 2000 compared to the previous decades and with the largest storage in the Southern Ocean. The first formal detection studies for ocean thermal expansion and glacier mass loss since the AR5 have confirmed the AR5 finding of a significant anthropogenic contribution to sea level rise over the last 50 years. New projections of glacier loss from two regions suggest smaller contributions to GMSL rise from these regions than in studies assessed by the AR5; additional regional studies are required to further assess whether there are broader implications of these results. Mass loss from the Greenland Ice Sheet, primarily as a result of increased surface melting, and from the Antarctic Ice Sheet, primarily as a result of increased ice discharge, has accelerated. The largest estimates of acceleration in mass loss from the two ice sheets for 2003-2013 equal or exceed the acceleration of GMSL rise calculated from the satellite altimeter sea level record over the longer period of 1993-2014. However, when increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions are taken into account, the net acceleration in the ocean mass gain is consistent with the satellite altimeter record. New studies suggest that a marine ice sheet instability (MISI) may have been initiated in parts of the West Antarctic Ice Sheet (WAIS), but that it will affect only a limited number of ice streams in the twenty-first century. New projections of mass loss from the Greenland and Antarctic Ice Sheets by 2100, including a contribution from parts of WAIS undergoing unstable retreat, suggest a contribution that falls largely within the likely range (i.e., two thirds probability) of the AR5. These new results increase confidence in the AR5 likel...

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“…Neither of our determinations attempt to discern the influence on GCMbased ΔT of natural variations such as ENSO, PDO, or AMOC. While the CMIP5 GCMs represent ENSO with some fidelity (Bellenger et al 2014), and changes in heat storage within the Pacific ocean simulated by GCMs has been linked to variability in ΔT on decadal time scales (Meehl et al 2011), these effects should appear as noise that is averaged out of the resulting signal, since our estimates of AAWR are based on analysis of 112 archived GCM runs. While GCMs might indeed have internally generated ENSO events or fluctuations in ocean heat storage that affect ΔT, the years in which these modeled events occur will bear no relation to the years these events occur in the real world (or in other models).…”

Section: Methodsmentioning

confidence: 99%

“…Various suggestions had been put forth to explain this apparent leveling off of ΔT, including climate influence of minor volcanoes Santer et al 2014;Solomon et al 2011), changes in ocean heat uptake (Balmaseda et al 2013;Meehl et al 2011), and strengthening of trade winds in the Pacific (England et al 2014). The major ENSO event of 1998, which led to a brief, rapid rise in ΔT due to suppression of the upwelling of cold water in the eastern Pacific, must be factored into any analysis of the hiatus.…”

Section: Global Warming Hiatusmentioning

confidence: 99%

Forecasting Global Warming

et al. 2017

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This chapter provides an overview of the factors that will govern the rise in global mean surface temperature (GMST) over the rest of this century. We evaluate GMST using two approaches: analysis of archived output from atmospheric, oceanic general circulation models (GCMs) and calculations conducted using a computational framework developed by our group, termed the Empirical Model of Global Climate (EM-GC). Comparison of the observed rise in GMST over the past 32 years with GCM output reveals these models tend to warm too quickly, on average by about a factor of two. Most GCMs likely represent climate feedback in a manner that amplifies the radiative forcing of climate due to greenhouse gases (GHGs) too strongly. The GCM-based forecast of GMST over the rest of the century predicts neither the target (1.5 °C) nor upper limit (2.0 °C warming) of the Paris Climate Agreement will be achieved if GHGs follow the trajectories of either the Representative Concentration Pathway (RCP) 4.5 or 8.5 scenarios. Conversely, forecasts of GMST conducted in the EM-GC framework indicate that if GHGs follow the RCP 4.5 trajectory, there is a reasonably good probability (~75 %) the Paris target of 1.5 °C warming will be achieved, and an excellent probability (>95 %) global warming will remain below 2.0 °C. Uncertainty in the EM-GC forecast of GMST is primarily caused by the ability to simulate past climate for various combinations of parameters that represent climate feedback and radiative forcing due to aerosols, which provide disparate projections of future warming.

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Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods

Cited by 645 publications

References 25 publications

Shifting patterns of mild weather in response to projected radiative forcing

Shifting patterns of mild weather in response to projected radiative forcing

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

Forecasting Global Warming

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